Ceramic materials find wide and diverse use in the fabrication of various types of elements and articles. Ceramic materials have found use in the fabrication of electrical components such as capacitors, and semiconductor device packages for supporting semiconductor devices. Such packages are comprised of a ceramic substrate with printed conductive metallurgy stripes connected to the device and to I/O pins or other connections which are joined to boards or the like. While many techniques are known for forming ceramic substrates for use in fabricating electrical components, one of the most popular procedures for such fabrication involves the casing of what is termed a "ceramic green sheet" and the subsequent processing and firing of the ceramic green sheet. Laminated multi-layer ceramic substrates provided with internal wiring are well known as illustrated and described in U.S. Pat. No. 3,564,114. Multi-layer ceramic substrates capable of mounting and interconnecting a plurality of semiconductor devices are well known and are described by an article entitled "A Fabrication Technique for Multi-Layer Ceramic Modules" by H. D. Kaiser et al in Solid State Technology, May 1972 P. 35-40. A sophisticated embodiment of a semiconductor package which embodies a multi-layer ceramic substrate is claimed and described in commonly assigned application Ser. No. 053,477, filed June 29, 1979 now U.S. Pat. No. 4,245,273. In this technology, green sheets of ceramic, i.e., ceramic powder held togther in sheet form by a temporary organic binder, are punched to form via holes, the via holes subsequently filled with a conductive paste, and metallurgy lines also formed on the surface, usually by screen printing. The conductive paste is formed of a refractory metal which will withstand the subsequent sintering process. The metallized sheets are stacked, laminated, and fired to form a monolithic multi-layer substrate with a complex internal electrical circuitry. This substrate structure is particularly advantageous since it affords an opportunity to do three-dimensional wiring in the substrate in what was normally waste or inaccessible space. The use of this waste space results in the creation of a high density sturdy electronic package with good performance and reliability. The fabrication of a multi-layer cercmic substrate, though simple in principal, is highly complex since the high temperature sintering process may cause reactions to occur between the components of the metallurgy and ceramic, and generate internal stresses which can cause de-lamination and cracking. As the substrate is cooled down from the sintering temperature, internal stresses are generated which can cause cracking and warpage if they are severe. This is due to different coefficients of expansion of the ceramic and conductive metal.
A desirable technique for mounting semiconductor devices on a multi-layer ceramic substrate is solder bonding the device to the substrate. In this technique, many solder pads on the surface of the device, are joined to a similar pattern of pads on the substrate. This requires a large number of closely-spaced via holes filled with conductive metal in the top layer of the substrate. A problem experienced in fabricating such a substrate is the formation of via-to-via cracks. These cracks are basically the result of thermal expansion mis-match between the conductive metal in the vias, and the ceramic material. Avoiding this thermal expansion mis-match is difficult because of the limited selection of conductive metals which will withstand the sintering temperature and also ceramic materials that will satisfy the demands of packaging.